Were the Birmingham Pub Bombings carried out by, or with the involvement of, agents of the British State?

One of the allegations made in the programme related to possible involvement of agents of the British State in terrorirst bombings carried out in Northern Ireland.

The programme also mentioned persistent obstruction by Police in Northern Ireland.

The programme also mentioned the huge number of informers etc in the terrorist community in Northern Ireland.

If agents of the British State were (allegedly) frequently involved in terrorist bombings (and other terrorist acts) in Northern Ireland, is there any reason to believe that such agents of the state weren't similarly involved in the Birmingham Pub Bombings?

In other words,

"Were the Birmingham Pub Bombings carried out by, or with the involvement or knowledge of, agents of the British State?".

That seems to me to be a question of momentous importance.

According to a recent response on Twitter from Justice for the 21, West Midlands Police obstructed investigation of the Birmingham Pub Bombings in 1974, 1975, 1988, 1989, 1993, c2001 and 2014.

Did West Midlands Police obstruct investigation of the Birmingham Pub Bombings in order to conceal involvement of agents of the British State in the deaths of 21 and injury of 182?

If West Midlands Police obstructed investigation of the Birmingham Pub Bombings would that be the only occasion when West Midlands Police has concealed terrorism by agents of the British State?

I believe not.

There is certainly, in my view at least, evidence suggesting that in 2014 Chief Constable Chris Sims and Assistant Chief Constable Marcus Beale failed to investigate alleged terrorist crimes by Prime Minister David Cameron and Secretary of State Michael Fallon.

If senior officers of West Midlands Police misconducted themselves in 2014 to conceal (alleged) terrorism offences by agents of the British State what reason is there to believe that West Midlands Police has not also concealed involvement of agents of the British State in the Birmingham Pub Bombings?

I intend to write to the West Midlands Police and Crime Commissioner regarding the perceived misconduct of Chief Constable Chris Sims and Assistant Chief Constable Marcus Beale.